The invention relates to a method for the manufacture of a piston, notably such as those employed in pressurized fluid actuators for the remote control of cocks, valves or the like.
Pistons of the type envisaged by the invention mostly comprise a head whose periphery ensures the guidance in the cylinder of the actuator. This head is rendered fast to means for transmitting the movement of the piston to an output shaft arranged transversely to the cylinder.
This is the case notably of rack pistons in which a piston end is fixed to the head and carries a rack arranged longitudinally with respect to the axis of the head to mesh with a pinion fixed to the transverse output shaft.
These pistons called single pistons, are generally mounted as an opposed pair in the same cylinder meshing with a single pinion.
The invention applies also to the manufacture of double pistons of the type contemplated in Applicant's French Patent Application No. 79/13337.
Such a double piston comprises two heads coupled together through at least one cross-member bearing the rack arranged longitudinally.
To manufacture notably single pistons such as defined above, it is known to manufacture them by forging or molding a blank which is then machined to produce the various support, guidance and seal-holding surfaces, as well as the rack.
This method is long, expensive and unprofitable on the mass production scale.
It is an object of the present invention to overcome these drawbacks by providing a method for the manufacture of pistons which is rapid, economical and particularly advantageous on the mass production scale.
It is also an object of the invention to provide a method for the manufacture of a piston, notably for actuating valves and the like. This piston comprises a head and at least one transmission member extending transversely with respect to the head.
According to the invention, the method is characterised in that a sectional element in bar form is taken whose profile envelops essentially that of the piston, then cutting up this profiled element into slices, the width of each slice being at least equal to the maximum diameter of the piston and removing by machining the material of the slice of the profiled element which extends relatively beyond the profile desired for the piston.
Thus, the often complex and difficult-to-machine surfaces bounding the profile of the piston are here obtained directly, or at least in blanks, by extrusion, whilst the surfaces of revolution around the axis of the head result from a simple inexpensive machining operation, for example turning.
This method hence considerably simplifies the machining operations necessary for manufacturing the piston, and dispenses also with forging or molding an initial blank, the latter being obtained according to the invention by slicing the profiled element.
Applicant has the merit of having developed a particulary economical method that the technician skilled in the art would have been dissuaded from applying, since it involves the removal of a relatively large amount of material by turning, and hence appears a priori expensive, but also and especially since it is contrary to the usual teachings to manufacture, starting from a profiled element, parts whose principal axis is perpendicular to the direction of extrusion.
Other features and advantages of the invention will emerge also from the following description relating to nonlimiting examples of its application.